title: Is referencing the posterior condyles sufficient to achieve a rectangular flexion gap in total knee arthroplasty?
abstract: Femoral malrotation in total knee arthroplasty causes flexion gap instability. Conventional instruments mostly reference the posterior condylar angle (PCA). The aim of this study was to verify whether the computer-navigated flexion gap (GAP) method produces a rectangular flexion gap and if a balanced flexion gap could also be achieved by referencing the PCA. A total of 100 knee prostheses were analysed using the navigated GAP method, and flexion gap symmetry along with femoral rotation were recorded. The GAP technique resulted in a rectangular flexion gap with adequate femoral rotational alignment. If the PCA technique had been used, only 51% of the femoral components would have been implanted in correct femoral rotation; the remaining 49% would have implanted with flexion gap instability. The GAP technique produces a rectangular flexion gap. The referencing of the PCA was shown to be less reliable. Thus, modern knee prosthesis instrumentation should not base femoral rotation solely on the PCA.
authors.affiliation: Rheinische Klinik für Orthopädie Viersen, Horionstrasse 2, 41749, Viersen, Germany. christophschnurr@gmx.de
authors.forename: Christoph
authors.initials: C
authors.lastname: Schnurr
authors.forename: Jochen
authors.initials: J
authors.lastname: Nessler
authors.forename: Dietmar Pierre
authors.initials: DP
authors.lastname: König
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001696:Biomechanical Phenomena; D017760:Bone Malalignment / Q000517:prevention & control; D005269:Femur / Q000033:anatomy & histology*; D006801:Humans; D007719:Knee Joint / Q000033:anatomy & histology* / Q000502:physiology* / Q000601:surgery; D007720:Knee Prosthesis; D010329:Patella / Q000033:anatomy & histology*; D011474:Prosthesis Design; D016059:Range of Motion, Articular / Q000502:physiology*; D012189:Retrospective Studies; D025321:Surgery, Computer-Assisted / Q000379:methods; D016896:Treatment Outcome